- #1
likephysics
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Homework Statement
This is not a HW question.
I was watching a lecture on youtube - http://www.youtube.com/watch?v=ke3SL_R92ys&NR=1
At 9mins into the lecture, there is a voltage divider equation.
(screen shot attached)
In the calculation of voltage at the +ve input of an op amp, the equation is
V+ = [(Vout-Vin)/(R1+R2)]R1+Vin
Why the Vin term at the end?
If you look at the feedback part as a voltage divider with 2 voltage sources, Vout at the top and Vin at the bottom. V+ would be I*R1
I = R1/(R1+R2) * (Vout-Vin)